This is a very common way to promote offers. For example, you will often see a blog post with links to certain products or services. If the reader clicks through and makes a purchase, the blog owner will make a commission. These in-text links blend in with other content on your site and are a great way of promoting an offer within your content, without being over-the-top salesy with banners.
Affiliate marketing is a very large industry and has become a key source of online income for many thousands of professional bloggers. With more and more online businesses becoming involved in affiliate marketing, more opportunities have arisen for bloggers, like you and I, to make money with their blog. and to ultimately create passive income streams.